Association of single umbilical artery with congenital malformations of vascular etiology

Postnatal development of fetuses with a single umbilical artery: differences between malformed and non-malformed infants

BACKGROUND

The presence of a single umbilical artery (SUA) is a fetal soft marker of congenital abnormalities. Among the most common related malformations, there are cardiological, nephrourological and digestive anomalies, most of which are considered to have a vascular etiology. There is an association between increased incidence of intrauterine growth retardation and adverse perinatal indicators, but whether this association is due to related anomalies or isolated SUA (iSUA) is controvisal.

METHODS

We reviewed 96 cases of iSUA and non-isolated SUA (niSUA), diagnosed in a period of two years in a referral hospital for high-risk pregnancies. Data on prenatal explorations, including fetal ultrasonography and karyotyping, were obtained. niSUA was diagnosed when no malformations were found prenatally or in postnatal evaluation.

RESULTS

Sixty-six newborns (68.8%) had no other anomalies and 30 (31.3%) presented with a variety of malformations including heart diseases, urophaties, digestive, nervous and musculoskeletal disorders, genetic abnormalities and complex malformations. Cardiological and nephrourological abnormalities were found to be the most frequent association with a SUA (both in 23.8% of malformed SUA newborns). Intrauterine growth restriction was not higher in iSUA newborns than in a normal population. Ultrasound allowed optimal prenatal diagnosis in most cases.

CONCLUSIONS

The prognosis of the fetus with a SUA is determined by the presence of other malformations observed by an expert sonographer. If no other findings are made, only a routine physical examination should be performed in newborns, but no other complementary examinations are required.

Two major patterns of nongenetic malformations are found at autopsy

Patterns of malformations seen in autopsies may contribute to the understanding of their pathogenetic mechanisms. Two entities, acardiac twins (ATs) and amniotic band disruption complex (ABDC), have distinct patterns, indicating different mechanisms, namely vascular perfusion deficit and external disruption. With ATs and ABDC as model groups, this study was undertaken to see if other dysmorphic infants with the characteristic defects of these models formed distinct and numerically important groups. A total of 192 autopsies with nongenetic malformations was divided into groups including (1) those with defects found in the ATs but not in the ABDC, (2) those with defects found only in the ABDC, and (3) those with a mixture of exclusive defects from each model group. The cases followed the characteristic defects of ATs or ABDC in 20% (group 1) and 28% (group 2), respectively, forming 2 large and distinct groups; only 4% had mixed malformations (group 3). Group 1 had different characteristics from group 2 as a result of the frequent multiple malformations, often with congenital heart defects (CHDs), internal and inferior malformations. These cases were probably related to a vascular perfusion deficit. Group 2 had a majority of females and single, external, and superior defects, but it lacked CHDs and inferior malformations. These cases were likely due to external disruption. Two large and distinct groups of autopsies with nongenetic malformations were thus identified, and their mechanisms are proposed to be similar to those of the model groups.

Indications for fetal echocardiography high referral, low yield?

An excellent imaging tool in the prenatal diagnosis and ongoing evaluation of congenital heart defects, fetal echocardiography is indicated in a selected population at increased risk compared with the general population. For certain "soft markers" of fetal congenital heart defects, ambiguity in the indications for fetal echo may result in a high referral rate, but low yield of congenital heart disease. Here, we critically examine 4 conditions, 2 maternal and 2 fetal: maternal gestational diabetes, advanced maternal age, isolated echogenic focus, and single umbilical artery. This critical review reveals that more prospective population-based studies with higher power and minimal bias need to be performed to establish the absolute risk of congenital heart defects in a selected population compared with that of the general population. Nonetheless, our analysis indicates that the absolute risk of congenital heart defects associated with each of these markers is low.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader should be able to define which patients should be referred for fetal echocardiography based on known risks, distinguish between relative and absolute risks for fetal congenital heart disease, and summarize fetal anomaly risks for women with altered glucose metabolism.

Squamous cell peritonitis associated with hydrometrocolpos in a multimalformed newborn

We present the case of a 1 day-old newborn with extensive squamous cell peritonitis resulting from vaginal atresia with hydrometrocolpos and squamous cell reflux through the genital system, a combination rarely recognized in the literature. Delivery was preceded by ultrasound diagnosis of oligohydramnios and "large bladder," the latter representing the dilated proximal vagina. Additional findings included paraesophageal hiatus hernia containing squames, urethral atresia, absence of vulva, lung hypoplasia, mild hypoplasia of the corpus callosum, and short umbilical cord with single umbilical artery (SUA). The possible relationship of the SUA with the constellation of infradiaphragmatic malformations is discussed.

Single umbilical artery: What does it mean for the fetus? A case-control analysis of pathologically ascertained cases

PURPOSE

To ascertain the frequency of chromosomal and other anomalies in fetuses with single umbilical artery.

METHODS

Placentas with single umbilical artery were identified from hospital pathology laboratory records. For each identified case, the next consecutive placenta with two umbilical arteries served as a control. Pathology records, maternal histories, and prenatal ultrasounds when available were reviewed for congenital anomalies, pregnancy complications, and maternal characteristics. When indicated, placental specimens, amniocytes, or neonatal bloods were karyotyped.

RESULTS

Single umbilical artery existed in 2.0% (97/4846) of pathological specimens. Fetuses with single umbilical artery had significantly more chromosomal (10.3% vs. 1.0%) and other congenital anomalies (27% vs. 8%).

CONCLUSIONS

The high incidence of major chromosomal and congenital anomalies justifies detailed fetal ultrasonography, echocardiography, and amniocentesis for karyotype when single umbilical artery is discovered during routine ultrasound.

Single umbilical artery and the VATER-animal model

BACKGROUND/PURPOSE

Vascular disruption is recognized as a cause of congenital malformations. The authors analyzed the significance of single umbilical artery (SUA) in the Adriamycin-animal model to find out if it was associated with organ malformations.

METHODS

Pregnant SD rats were injected with Adriamycin intraperitoneally at a dose of 2 mg/kg on days 6 through 9 of gestation. Serial transverse sections of full-term fetuses were analyzed by light microscopy. Embryos also were removed on different gestational days during organogenesis, and serial transverse histologic sections were examined and compared with suitable controls.

RESULTS

In experimental embryos (n = 47), presence of a SUA resulted from either persistence of the primitive umbilical arteries that joined each other ventral to the hind gut to give rise to one umbilical artery or from secondary atrophy of one of the definitive umbilical arteries. Malformations such as intestinal atresia were associated with anomalous fusion between the dorsal aorta and the persistent primitive umbilical arteries.

CONCLUSIONS

SUA is a prominent feature of the Adriamycin-animal model. No obvious association was found between malformations and SUA that resulted from atrophy of one of the definitive umbilical arteries; however, it was associated with anomalies such as intestinal atresia when it resulted from persistence of the primitive umbilical arteries.

Loss of Eph-receptor expression correlates with loss of cell adhesion and chondrogenic capacity in Hoxa13 mutant limbs

Mesenchymal patterning is an active process whereby genetic commands coordinate cell adhesion, sorting and condensation, and thereby direct the formation of morphological structures. In mice that lack the Hoxa13 gene, the mesenchymal condensations that form the autopod skeletal elements are poorly resolved, resulting in missing digit, carpal and tarsal elements. In addition, mesenchymal and endothelial cell layers of the umbilical arteries (UAs) are disorganized, resulting in their stenosis and in embryonic death. To further investigate the role of Hoxa13 in these phenotypes, we generated a loss-of-function allele in which the GFP gene was targeted into the Hoxa13 locus. This allele allowed FACS isolation of mesenchymal cells from Hoxa13 heterozygous and mutant homozygous limb buds. Hoxa13GFP expressing mesenchymal cells from Hoxa13 mutant homozygous embryos are defective in forming chondrogenic condensations in vitro. Analysis of pro-adhesion molecules in the autopod of Hoxa13 mutants revealed a marked reduction in EphA7 expression in affected digits, as well as in micromass cell cultures prepared from mutant mesenchymal cells. Finally, antibody blocking of the EphA7 extracellular domain severely inhibits the capacity of Hoxa13GFP heterozygous cells to condense and form chondrogenic nodules in vitro, which is consistent with the hypothesis that reduction in EphA7 expression affects the capacity of Hoxa13–/– mesenchymal cells to form chondrogenic condensations in vivo and in vitro. EphA7 and EphA4 expression were also decreased in the mesenchymal and endothelial cells that form the umbilical arteries in Hoxa13 mutant homozygous embryos. These results suggest that an important role for Hoxa13 during limb and UA development is to regulate genes whose products are required for mesenchymal cell adhesion, sorting and boundary formation.

Tracheoesophageal malformation: pathogenetic evidence provided by two cases

BACKGROUND

The aim of this observational study is to examine cases of upper respiratory atresia, in an effort to seek pathogenetic evidence suggestive of either a primary defect in embryogenesis or of a secondary etiology.

METHODS

Archival material of 412 fetal and perinatal autopsies with congenital malformations was reviewed in an effort to identify infants with complete upper airway obstruction without tracheoesophageal (TE) communication. Histological sections of the upper and lower respiratory tract were examined, seeking evidence of previous amniotic fluid or meconium aspiration, indicated by the presence of amniotic squamous epithelial cells, lanugo hair, or bile-stained meconium in the airways. Immunohistochemical stain for epithelial membrane antigen (EMA) and high-molecular-weight cytokeratin (CK1) were used to identify amniotic fluid and keratinizing squamous epithelial cells.

RESULTS

Eight infants with upper airway obstruction were identified, three of them without a TE communication. Two of the latter, one infant with multiple atresia born at 34 weeks gestation and another with tracheal atresia born at 32 weeks, presented evidence of amniotic fluid aspiration in their lungs.

CONCLUSIONS

Evidence of amniotic fluid aspiration in the above two cases indicates that there had been a previous patency of the upper respiratory pathway, since the absence of a TE fistula excludes any communication with the oronasal cavity. This implicates a secondary pathogenesis for at least some cases of upper airway obstruction.